1. Field of the Invention
The present invention relates to a damping method and a damping system for a hybrid vehicle in which a power unit consisting of an engine and a motor is supported in a vehicle body frame via an active vibration isolation support system, and vibration transmitted from the power unit to the vehicle body frame is damped by the motor and the active vibration isolation support system.
2. Description of the Related Art
Japanese Patent Application Laid-open No. 2003-113892 discloses an active vibration isolation support system that calculates a crank angular velocity from a time interval between crank pulses output every time a crankshaft rotates through a predetermined angle, calculates a crankshaft torque from a crank angular acceleration obtained by differentiating the crank angular velocity with respect to time, estimates an engine vibration state as a variation in the torque, and controls the supply of current to a coil of an actuator according to the engine vibration state, thus exhibiting a damping function.
Also, Japanese Patent Application Laid-open No. 2001-57709 discloses a hybrid vehicle equipped with an engine and a generator/motor as power sources for travel in which, when the generator/motor is operated as a motor or a generator while the engine is running, by making the generator/motor generate a damping torque that counteracts vibration of the engine, that is, torque variation of a crankshaft, the vibration transmitted from the engine to the vehicle body frame is damped.
In the hybrid vehicle in which the engine equipped integrally with the generator/motor is supported in the vehicle body frame via the active vibration isolation support system, since the damping force generated by the generator/motor and the damping force generated by the active vibration isolation support system are conventionally controlled independently, control by one might interfere with control by the other, so that a sufficient vibration damping effect might not be obtained. Furthermore, more electric power is consumed by the generator/motor for damping than is consumed by the active vibration isolation support system, and with the conventional control has a possibility that the power consumption of the generator/motor might increase more than necessary.